Check if parenthesis are balanced problem with * (Typescript)

My solution to a “Daily Coding Problem” that I received in my mail today.

You’re given a string consisting solely of (, ), and *. * can represent either a (, ), or an empty string. Determine whether the parentheses are balanced.

For example, (()* and (*) are balanced. )*( is not balanced.

Here’s my solution in Typescript,

oneFortyTwo(str: string): boolean {
        if(str == undefined || str == null) {
            return false;
        }
        //not sure if this is right?
        if(str.length == 1){
            return false;
        }
        let balanced: boolean = false;
        let parenStack = new Stack<string>();
        for(let i=0; i < str.length; i++) {
            let char = str.charAt(i);
            let topChar = parenStack.peek();
            if(topChar == null) {
                parenStack.push(char);
            } else {
                if(topChar == "*") {
                    parenStack.pop();
                } else if((char == "(" || char == "*") && (topChar == ")" || topChar == "*")) {
                    parenStack.pop();
                } else if((char == ")" || char == "*") && (topChar == "(" || topChar == "*")) {
                    parenStack.pop();
                } else {
                    parenStack.push(char)
                }
            }
        }
        return parenStack.isEmpty() ? true: false;
    }

I know, it wasn’t exactly super essential but I wrote the code for a custom Stack class anyway.

class Stack<T> {
    data:Array<T> = [];
    constructor(){
        this.data = new Array<T>();
    }
    isEmpty(): boolean {
        return (this.data.length == 0);
    }
    getSize() {
        return this.data.length;
    }
    push(elem:T) {
        this.data.push(elem);
    }
    pop() {
        return this.data.pop();
    }
    peek() {
        if (this.data.length > 0) {
            return this.data[(this.data.length - 1)];
        } else {
            return null;
        }

    }
}

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